7 - The Discovery of a New Organ: The Parathyroid Gland

Summary

The Discovery of the Parathyroid and Its Function

The parathyroid gland was only discovered as an anatomically and functionally distinct organ through resection and transplant experiments in animals. Tetany, the specific symptom associated with the failure of the parathyroid, had often been observed after goiter operations and experimental thyroid removals, but since no one knew this organ existed, many researchers attributed tetany to the removal of the thyroid gland itself. Especially after experimental thyroid removal in animals, tetany was the first and predominant symptom. Cachexia strumipriva, the longterm side effect of total thyroidectomy that Kocher observed, was sometimes even overlooked because tetany was so much more dramatic. If researchers became aware of both symptoms, they often conflated them and interpreted tetany as the immediate consequence of thyroidectomy and cachexia as its long-term effect. The discrepancy between tetany and cachexia was a weak point in the theories about thyroid function. The two clinical pictures seemed too different to attribute to the absence of the same organ. The tetanic symptoms in particular suggested “wound reflexes” caused by neural damage. Thus Kocher’s opponent Hermann Munk, for example, did not regard tetany as a specific side effect of organ removal but as the consequence of nerve damage during surgery.

These phenomena became easier to understand once doctors and scientists began to distinguish the parathyroid glands (also called epithelial bodies) from the thyroid gland proper. At first the term “parathyroid” simply referred to the thyroid tissue found outside the main organ, even though the two organs had already been identified as anatomically separate in several studies on animals, including the work of British surgeon and natural scientist Richard Owen on the rhinoceros in 1852, and Swedish anatomist Ivar Sandström on the dog and then in other animals and humans in 1877. Sandström, often regarded as the discoverer of the parathyroid, assumed on the basis of the histological structure of these entities that they were embryonic thyroids and called them “glandulae parathyroideae.”

The choice of the animal used for experiments turned out to be important. For instance, no fatal tetanies were observed after radical thyroidectomies in rabbits.